Telegraph signal regenerating apparatus



Oct. 24, 1933. R D SALMON 1,931,876

TELEGRAPH SIGNAL REGENERATING APPARATUS Filed Sept. 24, 1930 FIGI.

INVE NTOR REGINALD D.SAL.MON

ATTORN Y Patented Oct. 24, 1933 UNITED STATES TELEGRAPH SIGNALREGENERATING APPARATUS Reginald Dennis Salmon, Croydon, England, as-

signor t Creed and Company Limited, Croydon,

I Surrey, England Application September 24, 1930, Serial No. 484,075,and in Great Britain January 21,

13 Claims. (01. 178-695) This invention relates to signal regeneratingapparatus in telegraphic systems in which changes of line currentconstituting thesignals .are originated at definite multiples of aunitary 6 element of time.

In telegraphic systems of this class it is a great advantage to employmeans capable of independent harmonic motion in signal receiving andreproducing apparatus and to synchronize 10 this harmonic motion to thatof the unitary elements of the signals. Suitable small portions of thereceived signals can be selected thereby at definite regular intervalsto determine the method is to employ a rotating shaft. The principle,however, is the same and essentially consists of means to efiectoperations at regular cyclic intervals. In this manner signals can bereproduced free from the distortion, attenuation and otherirregularities attendant on transmission over a line.

The methods of synchronizing the harmonic motion of the signalregenerator to the received signals may consist of sending at regularspaced intervals a special synchronizin impulse from the transmittingapparatus, which is utilized to eiiect a correcting tendency on theharmonic motion of the regenerator to bring it into the desired phaserelation with the received signals.

Synchronization may also be eiiected through the medium or the receivedsignals themselves. A telegraphic signal synchronizing apparatus of thislatter class and in which the synchronized member consists of a rotatingshaft is shown 4.0 in British Patent No. 368,672. A telegraphic signalregenerating apparatus in which a rotating shaft synchronized withreceived signals is employed to' select small portions of the receivedsignals and to reproduce them in regenerated form is shown in BritishPatent 309,388.

A common feature of all these methods of signal synchronization andregeneration is that operations are required to: be effected inaccordance with the polarity or character of received signals atrecurrent short intervals of time. The

length or" the interval of time required for an operation in one manneror another is determined by the polarity and character of the signalduring that interval. The smaller this interval the greater will be themargin of tolerance.

til

In the case of a synchronizer, for example, the phase of the regeneratoris constantly oscillating between lagging and leadingrelative to meantrue synchronism with the received signals. At correct phase relationthe correcting means tend- 9 ing to bring the phase of the regeneratorinto synchronism with the received signals is unaffected. It isnecessary for the phase difference to exceed a certain amount in orderto actuate this correcting means. The smaller this amount necessary thegreater will be the degree'of synchronization attainable. In the case ofa signal reproducer it will be seen-that the smaller the portioncorresponding to the true mean centre of a received signal necessary toselect the char- 7! I acter of the'reproduced signal, thegreater will bethe margin for distortion of received signals. This distortion as isknown, is permissible on the boundaries of each signal element up to thelimits of that middle portion reserved for selecting the reproducedsignal element.

The apparatus shown in the specifications hereinbefore mentioned effectsby mechanical means the operation of contact lovers to one position oranother by momentary actuation of abutment devices. To obtain thenecessary duration of contact to effect the operation of means such aselectromagnetic relays connected thereto, local holding means such as aspring-pressed jockey roller riding on a knife edge formed on thecontact lever is employed. The present invention permits a high speed ofoperation by electrical methods, in which means connected in the anodecircuit or" a thermionic valve effects each operation in accordance withthe potential 9 of the grid resulting from a. charge communicated to thegrid circuit during a very brie contact period.

The sustained effect on the anode current of a three electrode valve dueto the charging of the grid circuit when sufficient, capacity isassociated with the grid circuit to maintain the grid at a potentialwhich is substantially constant for a period following the charging ofthe grid circuit, is known. The present invention applies this principleto telegraphic regenerating apparatus in which operations are effectedin accordance with the polarity or character of received signals entinvention therefore, consists of telegraphic synchronizing apparatus inwhich the essential elements comprise cyclic switch means locally timedand alternately selecting one of two potentials, switch means timed byreceived signals to charge the grid circuit of a thermionic valve inaccordance with the selected potential, means responsive to change ofanode current said thermionic valve consequent upon said charge of thegrid circuit, and means operated thereby tending to adjust the localtiming of said cyclic switch means tothat of said received signals. 7

Another feature consists of telegraphic signal reproducing apparatus inwhich the essential elements comprise means responsive to receivedsignals to select one of two potentials, cyclic switch means maintainedin synchronism with received signals to charge the grid circuit of athermionic valve in accordance with the selected potential in a briefinterval corresponding to the mean centre of each received signalelement, means responsive to change of anode current of said thermionicvalve consequent upon said charge of the grid circuit, and meansoperated thereby to reproduce said received signals.

Another feature consists of employing a rotating shaft to effect cyclicswitching operations for maintaining synchronism with received signalsand for reproducing said .received signals in regenerated form.

7 Another feature is that means is employed for adjusting the phaserelation between cyclic switching operations for maintaining synchronismand cyclic switch operations for the re-' producing signals inregenerated form. If a rotating synchronized shaft is employed forexample, the cam members or the commutator switching members for the twoswitching opera-- ticns respectively may be adjusted relatively on theshaft. Alternatively, one set of switching members or brushes, accordingto the'means employed, which cooperate with the rotating shaft may beadjusted angularly while the other set remains fixed. By this means whensynchronism is attained the middle portions of the received signals maybe, selected.

Another feature consists of incorporating a mechanical relay intelegraphic synchronizing and reproducing apparatus in which a rotatingshaft is employed to effect cyclic switching operations, the mechanicalrelay effecting switching operations timed by and responsive to receivedsignals.

Still another feature consists of employing insulating drums carryingsuitable metal inserts and upon which drums are stationary brushesadapted to effect cyclic switching operations during the rotation of ashaft. Other features will be evident from. the following descriptionswhen taken in conjunction with. the accompanying drawing in which Fig. 1represents diagrammatically and by way of example a telegraph signalregeneratorin which both means for synchronizing and means forreproducing regenerated signals are arranged according to the presentinvention. Fig. 2 illustrates details of a rotary switching means foradjusting phase.

Referring to Fig. 1, a shaft 1 is driven through a variable speed gearcomprising isc Z and friction wheel 3, from a motor l which is under thecontrol of one or the other of two speed governors 5 and 6. With a shuntwound motor as shown, governor 5 would be adjusted to govern the speedof the motor so that shaft 1 rotates about faster than true synchronousspeed of the incoming signal elements when under the control of thisgovernor. Governor 6 would be likewise adjusted so that shaft 1 rotatesabout /2% slower than true synchronous speed when under the control ofthis governor.

It will be noted that with the arrangement as shown of a shunt woundmotor and governing by means of short circuiting a resistance in serieswith the field winding when the governed speed is exceeded, if bothgovernors 5 and 6 are connected in parallel with this resistance themotor will be governed by governor 6 at the lower of the two speeds. Ifthe circuit through governor 6 is broken the motor speed increases untilthe other governor 5 functions at the higher speed. Any convenientmethod, however, may be adopted for driving shaft 1 at one or other oftwo ground speeds: the precise arrangement forms no essential part ofthe present invention.

Shaft 1 actuates two circuit controlling devices represented in thiscase as commutators 7 and 8 consisting of two insulating drums eachcarrying a suitable inserted metal conductor and upon which drumsstationary brushes 9-13 are arranged to hear. The inserted metalconductor in commutator, 7 is so arranged that during one halfrevolution, brush 10 is electrically connected to brush 9 and insulatedfrom brush 11: during the other half revolution brush 10 is connectedtobrush 11 and insulated from brush 9. ,Comrnutator 8 consists of aninsulating drum carrying an axially arranged inserted metal bar 34 (seeFig. 2) The an ular width. of the metal bar and the correspondingangular bearing surfaces of the brushes 12 and 13 are made small so thata very brief interval of electrical connection is effected betweenbrushes l2 and 13 at each revolution of the shaft 1. Contact springsactuated by suitably contoured cams may if desired replace theconnnutators as above .described or any other forms of suitable circuitcontrolling devices actuated by shaft 1 may be substituted. Theessential requirement in the first mentioned case is to effect a changeover in connection from one: circuit to another at each half revolutionof shaft 1 and 2, in the second mentioned case a very brief interval ofcontact is made once in each revolution of shaft 1. In both cases,switching operations are eifected, timed by the rotating shaft.

15, 16, which are 99 out of phase for actuating contact arms 1'7 and 18respectively may conveniently, though not essentially, be driven fromshaft 1. The escapement or clutch controlling member of the mechanicalrelay is actuated by the armature 20 of an electro-magnetic relay 19which is responsive to received signals. At each actuation of thearmature 20, the driven member of the clutch of the mechanical relayrotates half a revolution and eccentric 16 thus actuates contact lever18 from one extreme position to another, to make contact with contactscrew 21 and 22 according to whichever side armature 2-3 of relay 19 isactuated. Ateach actuation of armature 20 moreover, the second eccentric15 of the mechanical relay actuates contact lever 17 to make momentarycontact with one or the other of contact screws 23 and 24;. This, asstated, is effected by eccentric 15 which is 90 out of phase witheccentric 16. It will be seen therefore that the normal position of restof contact lever 17 is midway between contact screws 23 and 24, whilethe normal position of rest of contact lever 18 is against contact screwA mechanical relay 14 having two eccentrics Jio Lao

21 or 22. The function of contact levers 1'7 and 18'actuated by themechanical relay upon response of the electromagnetic relay 19 is toactuate circuit controlling devices at each change in polarityor-character of theline current .constituting the received signals. Thecircuit controlling device'l'l closes a circuit at periods determined bythe instants at which the received signals change polarity or character,while the circuit controlling device 18 relays the signals as receivedby relay 19. It is not essential that these operations be effected by amechanical relay as shown: other methods may be adopted as will beapparent to those skilled in the art. The essential feature is thatswitching operations are effected, timed by the signals as received.

Each of thetwo commutators'l and 8 actuated by the shaft 1 is associatedthrough contact levers 17 and 18 respectively with one of two threeelectrode thermionic valves 25 and 26. A grid battery27, opposite polesof which are connected-to brushes 9 and 11 is joined by one pole, inthiscase from brush 11 to thegrid of valve '25. Brush 10 is connected tocontact lever .17, and contact screws 23 and 24 are commoned andconnected to the filament of this valve 25. A condenser 28 of a suitablevalue is connected between the grid and filament to give this gridcircuit sufiicient capacity for the purpose hereinafter mentioned. Anelectromagnetic relay 29 in theanode circuitof valve 25 is adapted toactuate its contact tongue from one side to the other :in accordancewith the variations of anode current supplied by the high tensionbattery 30. The contact tongue of relay 29 alternately opens and closesthe circuit through governor 6 of .filamentof valve 26. Brush 13 ofcommutator "8 is connected to the grid of valve 26 and a condenser 32 ofa suitable value is connected'in this grid circuit. An electromagneticrelay 33 in the anode circuitactuates its contact-tongue in accordancewith the variations of anode current and repeats theregenerated signalstoline as shown, .or may be utilized to operate local signal recordingmeans.

The arrangements as described are purely schematic, the principleinvolved'will be seen in either case to consist of charging the gridcircuit of either valve to one of two potentials. For the synchronizingvalve 25 the potential is selected by commutator land impressed whencontact lever 1'7 makes contact with either of contact screws 23 and'24.For the signal regencrating valve 26, the potential is selected by con-.tactlever 18 and impressed when commutator 8 .makesmomentary contact.The capacity ofthe grid circuitof eachvalve 'is adjusted by condensers28-and 32 respectively so that the grid which in each case is charged toone or the other potential in a very brief interval of time, main-'tains that potential substantially unchanged over an interval of time.This permits the corresponding electromagnetic relay in the anodecircuit to be actuated to one side or theother in accordance with thestrength'of the anode current when the grid is substantially at eitherof these two potentials. e

.- The whole arrangement forms a device whereby :the rotating. shaft 1is maintained in synchronism with :theincoming signals, the phaseof theshaft lower of the two speeds.

commutator 7 so that the contact bar passesunder the brushes '12 and 13at the instant in each revolution of shaft '1 which corresponds 'tothetrue mean centre of each received signalelement. 'If

shaft 1 is in its exact synchronous positionzbrushes '9, 10 and 11 willbe momentarily connected together at the instant-contactlever 17 touchescontact screw 23 or 24 consequent upon-the actuation of armature 20 toone side or the other in response to the character of a received signal.It will be noted that this instant is not necessarily the same instantat which the armature 20 is actuated, for the mechanical relay has asmall but definite time lag. The eifect'is the same, however, as will beseen. If the shaft 1 is ahead of its correct position, one'brush, 9forexample, will be connected to brush 10 at .the instant contact lever1'7 is actuated. The grid circuit of valve 25 is thereupon charged sothat the grid is negative to the filament, the anode current is reducedand the armature of relay 29 joins governor 6 in circuit with motor 4 sothat the speed of shaft 1 thereupon drops from above true synchronousspeed to /2 below. The motor continues to be governed at the lower ofthe two speeds until the phase of shaft 1 has fallen behind its truesynchronous positions. When this occurs brush 11, instead of brush 9will be connected to brush 10 at the instant contact lever 17 is actuated. Then battery 27 applies no potential to the grid of tube 25.This potential, however, when compared to the former negative potentialmaybe considered as a relatively positive potential. Furthermore, inaccordance with well-known or conventional tube circuits, a positivepotential may be momentarily impressed'on the grid of tube 25 from thepositive terminal of the battery used toheat the filament of this tube.Since condenser 28 is short circuited at the instant contact lever 17 isactuated the above circuits will then be completed and a correspondingpotential will be applied to the grid of tube 25. This will result in anincrease of the anode currentand a consequent actuation of the armatureof relay 29 to its open position. This opens the circuit throughgovernor 6 and the motor 4' is thereafter governed by the other governor5' at the The phase of shaft 1 therefore picks up again'and the actionis such as to maintain this phase constantly oscillating, slightly fromlagging to leading and vice versa with respect to the signal periods asrepresented by the actuation of armature 20 of relay 19.

As already stated, the grid circuit of valve 26 is completed throughbrushes 12 and 13 at the instant which represen's the true mean centreof the received signal element. The polarity .to which the'grid ischarged is determined by the position of contact lever 18 whichhas'already. been actuated to contact screw 21 or 22 accordingv to thepolarity or character of the signal. Relay 33 is thereafter actuated toone side or the other according to the strength of the anodecurreht andreproduces each signal element in regenerated form free of. distortion.

What is claimed is: I

1. In a telegraph system, synchronizing apparatus comprising meansproviding twodiiferent potentials, a thermionic valve, cyclic switchmeans locally timed and adapted alternately :to select one and then theother of said potentials, switch means timed by received signalstocharge thegrid circuit of said thermionic valve :in Laocordance withthe selected potential, relay means responsive to change of anodecurrent consequent upon said charging of the grid circuit, said relaymeans being operatively associated with speed Varying means forcontrolling the timing of said cyclic switch means in accordance withthat of said received signals.

2. Telegraph synchronizing apparatus comprising a rotatable shaft,driving means therefore, switch means operated and timed by saidrotatable shaft to select alternately one and then the other of twopotentials, other switch means timed by and responsive to receivedsignals to charge the grid circuit of a thermion c valve in accordancewith the selected potential, relay means responsive to the change ofanode current consequent upon said charging of the grid circuit, andspeed governing means controlled thereby to maintain said rotatableshaft in synchronism with received signals.

3. Telegraph signal regenerating apparatus comprising a rotatable shaft,driving means therefor, switch means operated by said rotatable shaft toselect alternately one and then the other of two potentials, otherswitch means operated by said rotatable shaft to close a circuit forbrief intervals corresponding to the mean centres of received signalelements, signal responsive means, switching means operated thereby toclose a circuit at brief intervals corresponding to the timing ofchanges in the character of the received signals, other switching meansoperated by said signal responsive means to select one or the other oftwo potentials in response to received signals, thermionic valve meanscontrolled by said potentials, speed governing means controlled by saidvalve means to maintain said rotatable shaft in synchronism with thereceived signals and signal reproducing means also controlled by saidvalve means to reproduce the received signals in regenerated form.

l. In telegraph signal regenerating apparatus, a rotatable shaft,driving means therefor, switch means operated by said rotatable shaft toselect alternately one and then the other of two potentials, speedgoverning means controlled thereby to maintain rotatable shaft isynchronism with received signals, ofher switch means also operated bysaid rotatable shaft to close a circuit at brief intervals correspondingto the timing of the changes of character of the received signals,signal reproducing means controlled by the last mentioned switch means,and means to adjust the phase relation between the operation of the twoswitching means efiected by said rotatable shaft.

5. In telegraph synchronizing apparatus, a rotatable shaft, drivingmeans therefor, a speed governing device adjusted to efiect rotation ofsaid shaft at a speed slightly above true synchronous speed withreceived signals, a second speed governing device adjusted to effectrotation of said shaft at aspeed slightly below true synchronous speed,a relay responsive to received signals, switch means operated by saidshaft to select one or the other of two potentials at each response ofsaid relay and means controlled thereby to render one or the other ofsaid speed governing devices operative upon said driving switch meansoperated under control of received signals by said rotary shaft tocharge the grid circuit of said thermionic valve in accordance with theselected potential, relay. means responsive to the change of anodecurrent consequent upon said charging of ,the grid circuit and'speedgoverning means controlled thereby to maintain said rotary shaft insynchronism with received signals.

7. In telegraph reproducing apparatus, a thermionic valve, anelectromagnetic relay responsive to the character of received signals, ashaft rotating in synchronism with the received signal elements, amechanical relay operated by said shaft .under control of saidelectromagnetic relay to select one or theother of two potentials,

switch means also operated by said shaft to close a circuit at briefintervals corresponding to the mean centre of each signal element, andthereby to apply the selected potential to said valve only during saidbrief intervals of time.

8. In combination, a rotaryv shaft, alternate switching means andcircuit closing means operated thereby, signal responsive means, meansyieldingly driven by said shaft and controlled by said signal responsivemeans and circuit closing and'alternate switching means operated therebyto' maintain said shaft in synchro-nism with received signals and toreproduce said signals in regenerated form. v

9. In signal regenerating apparatus, a rotary shaft, three stationarybrushes, an insulating cylindrical drum associated therewith and carriedby said shaft, commutating metal inserts in said cylinder to arrange andto connect said brushes alternately in pairs at each half .revolution ofsaid shaft, a second insulating cylindrical drum carried by said shaft,a narrow longitudinally extending metal insert therein, two brushescooperating therewith to effect simultaneously a brief interval ofcontact and once in each revolution of said shaft, and means to adjustthe period in which said brief interval'of contact is made relatively tothe period of connection in pairs of the three brushes aforesaid.

10. In signal regenerating apparatus a mechanical relay comprising meansresponsive to the character of received signals, an escapeinent actuatedthereby, a rotatable member released for half a revolution at eachactuation of said escapement, two eccentrics relatively displaceddegrees on said rotatable member,- a contact tongue actuated by oneeccentric from a mid position to make contact at the extreme positions,and a second contact tongue actuated by the second eccentric from oneextreme position to the ther at each said half revolution.

ll. In a telegraph system, synchronizing apparatus comprising a relayresponsive to receive signals, an escapement actuated thereby, arotatable member releasable for half a revolution at each actuation ofsaid relay, an eccentric carried by said rotatable member, a rotatableshaft having yielding driving engagement with said rotatable member,motor means for rotating said shaft approximately in synchronism withreceived signals, speed regulating means forsaid motor means having twoalternative limiting speeds respectively above and below the synchronousspeed, a thermionic valve, means providing two different potentials, aswitch device carried by said'rotatable shaft arranged to closealternate contacts during successive half revolutions to render saidpotentials alternately available for application to the grid circuit ofsaid valve, switch means operatively connected with said eccentric formomentarily closing said circuit during each half revolution thereof andrelay means responsive to changes in the anode current of said valve andoperatively associated with said speed regulating means to determine theeffective limiting speed thereof.

12. In a signal regenerating apparatus a relay responsive to receivedsignals, an escapement actuated thereby, a rotatable member releasablefor half a revolution at each actuation of said relay, two eccentricsrelatively displaced 90 degrees on said rotatable member, a rotatableshaft having yielding driving engagement with said rotatable membermotor means for rotating said shaft approximately in synchronism with.received signals, a thermionic valve, means providing two differentpotentials, a switch device carried by said shaft arranged to. closealternate contacts during successive half revolutions to render saidpotentials alternately available for application to the grid circuit ofsaid valve, switch means operatively connected with one of saideccentrics for intermittently closing said circuit, relay meansresponsive to change of anode current of said valve, a speed governorfor said motor means responsive to said relay means to change thelimiting speed of said motor means above or below the synchronous speed.A second thermionic valve a second switch device carried by the shaftand arranged to close during a short interval of each rotation of saidshaft corresponding approximately to the middle of each signal period,switch means operatively connected with the other of said eccentrics forreversing the polarity of potential applied to the grid circuit of saidsecond thermionic valve, and signal relay means responsive to changes ofanode current of said second thermionic valve.

13. In a telegraph system, a rotating shaft, switch means on said shaftfor selecting one at a time, each one of a plurality of cyclicallyselectable potentials, other switch means responsive to received signalsto charge the grid of a thermionic valve in accordance with the selectedpotential, and speed controlling means responsive to the change of anodecurrent consequent upon the charging of said grid for maintaining theshaft rotating in synchronism with received signals.

REGINALD DENNIS SALMON.

